2005-05-18 04:00:00 PDT Washington -- The Senate will open a constitutional showdown over President Bush's judicial nominees today that could undermine minority power in the Senate and could have huge political fallout for both parties, though no one yet knows what kind.

Senate Majority Leader Bill Frist, a Tennessee Republican with presidential ambitions, is expected to bring one of four contested nominations to the floor of the Senate today. The maneuver could be the first step in an attempt by Republicans to end using the filibuster to block judicial nominees.

Central to the conflict are California Supreme Court Justice Janice Rogers Brown, nominated for the District of Columbia Court of Appeals, just a step below the Supreme Court, and Texas Supreme Court Justice Priscilla Owen, nominated for the Fifth Circuit appellate court in New Orleans.

Both women could win a majority of the Republican-controlled Senate for confirmation but have been blocked by Democratic filibusters.

Brown walked surrounded by Senate aides through the halls of the Capitol Tuesday on her way to a photo session with Frist and Owen. The California judge smiled stiffly but was mute to questions about becoming the center of a Senate storm that could alter the balance of power among the three branches of government by strengthening the executive at the expense of the Congress.

The filibuster, a Senate tool used by the minority to block legislation, requires 60 votes to break, and Republicans have only 55 seats in the 100- member Senate. During Bush's first term, Democrats filibustered 10 of the president's 52 appellate court nominees. Seven of those 10 are again at issue.

The proposed action in the Senate is the latest escalation of a feud over the judiciary dating to President Ronald Reagan's failed nomination of Judge Robert Bork to the Supreme Court and involving more than 60 nominees of Democratic President Bill Clinton that were blocked by Republicans.

Frist is likely to wait a day or so before attempting to break a filibuster on the nomination of Owen or of Brown, whichever he chooses to take to the floor first. That vote to end debate, known as cloture, could occur Monday or, aides said, more likely Tuesday. Republicans are expected to fail to obtain the 60 votes necessary to move on to a straight up-or-down vote on the nominee.

At that point, Frist is expected to set in motion a series of parliamentary moves to clear the way for an up-or-down vote -- and ban filibusters against judicial nominees.

Democrats said they would retaliate by stopping action on Republican legislation, though they have backed off earlier threats to bring the Senate to a standstill.

The confrontation is aimed at the Supreme Court, where Chief Justice William Rehnquist is ailing from cancer and is expected to step down this year. Rehnquist's replacement by another conservative would not alter the fragile ideological balance of the court, which often splits 5-4.

The courts are enormously influential in shaping American life, particularly the Supreme Court, the court of last resort. Religious conservatives and liberal interest groups are exerting tremendous pressure on both parties in the Senate to hold the line.

But both parties have a huge stake in later potential vacancies to be left by other aging justices during Bush's second term. Two considered likely to retire soon are a liberal justice, 85-year-old John Paul Stevens, and a moderate swing justice, Sandra Day O'Connor.

A Senate Republican aide said Owen was likely to be the first nominee raised for a vote, having been blocked the longest -- four years as of last Monday. Brown, a vociferous conservative and daughter of a black sharecropper, has been on hold since 2003.

The Senate has been roiled by the filibuster issue in part because it is a legislative body in which informal agreement and collegiality move the agenda.

Independent negotiations to avert the showdown continued Tuesday among a dozen moderates in both parties, led by Sens. Ben Nelson, D-Neb., and John McCain, R-Ariz.

McCain is one of three Republicans, along with Sens. Olympia Snowe of Maine and Lincoln Chafee of Rhode Island, who have said they will side with Democrats.

Snowe said she believed it was "more likely than not" that they could prevail in efforts to get six Republicans to refuse to support Frist in his efforts to change Senate rules and six Democrats to abandon their leadership to vote to end filibusters on current and future Bush nominees in all but extreme circumstances.

By depriving both parties of the votes to achieve their aims, the hope is to avert the confrontation.

"It's a pivotal moment, I think, in the history of this institution," she said.

Many Republicans, despite their anger at Democrat efforts to block Bush nominees, have expressed misgivings about overturning Senate precedent.

The filibuster gives significant power to the minority party, and many scholars contend that it's a critical element of the constitutional system of checks and balances among the branches of government.

Removing the right to filibuster judicial nominations would strengthen the hand of all presidents to shape the courts and would reduce the pressure to negotiate with the minority party about such nominations.

Republicans have promised to contain the "nuclear option" to judicial nominees, but Democrats warn that once the new precedent is set, it can easily migrate to other presidential nominations and even legislation. Almost no Republicans have said they want to remove the right to filibuster legislation.

Sen. Dianne Feinstein, D-Calif., warned last week in an exhaustive discourse on the Senate floor that once the rule on filibusters was broken, "it will be hard to limit and hard to reverse."

Sen. George Allen, a Virginia Republican who spearheaded the election drive that gave the GOP four new Senate seats last November, said forcing votes on the nominees would be a political winner for Republicans.

"I've seen the reaction in the Carolinas, Florida, Louisiana, Oklahoma, South Dakota and Alaska," Allen said. "This is a very big issue to the people who elected us.

"I do not think we ought to be timid. We should not cower. We need to go for it." Allen predicted Democratic threats to shut down the Senate would backfire.

"I think we have to call their bluff," he said. "They recognize this kind of approach is just leading them into a political box canyon where they dig themselves in a deeper political grave."

But Montana Democratic Sen. Max Baucus said Democrats were willing to carry out delaying tactics indefinitely.

He called the nuclear option "profoundly detrimental to the country" and warned that the extent of the damage might not be known for years. Frist will go down in history, he said, as the majority leader who weakened the Senate and made it a clone of the House, where the majority pushes through legislation at will.

"It is wrong to break the rules to change the rules," said Baucus, a moderate who helped Bush pass landmark tax cuts and Medicare legislation during his first term. "That's what dictators do in Third World countries."

Fight over the filibuster

What is it?

A filibuster is a Senate tactic in which the minority party prolongs debate to delay or prevent a vote on a measure it opposes.

How are filibusters ended?

Ending a filibuster requires a vote of at least 60 senators.

What's ahead?

Republicans are expected to bring one of four contested judicial nominations to the Senate floor today. If Republicans can't force a straight up-or-down vote, Senate Majority Leader Bill Frist is expected to employ a series of parliamentary maneuvers that would ban filibusters against judicial nominees.

Why is this called the 'nuclear option'?

The move would ban the use of an established legislative tool and could have a significant effect on the way the Senate works.